Simplify the following expression: $n = \dfrac{6}{7t} - \dfrac{3}{2t}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $7t$ and $2t$ $\lcm(7t, 2t) = 14t$ $ n = \dfrac{2}{2} \cdot \dfrac{6}{7t} - \dfrac{7}{7} \cdot \dfrac{3}{2t} $ $n = \dfrac{12}{14t} - \dfrac{21}{14t}$ $n = \dfrac{12 -21}{14t}$ $n = \dfrac{-9}{14t}$